Prism glasses, and particularly glasses made only of plastic or non metallic, non-ferrous (non-magnetic) material, are used in many situations including, but not limited to, reducing the claustrophobic feeling when a user is subjected to an MRI procedure. During this procedure, the user typically lies flat on his or her back and his or her body is inserted either feet first or head first into a large cylindrical MRI container which generally makes considerable noise during the MRI procedure. When the user wears prism glasses, the user can see either images downward at the user's feet or upward beyond the user's head. Technicians may converse with the users or the users may view a film or other visual distraction at the user's feet or beyond the user's head. Of course, if the user is lying on his or her back, the image is “down” in the direction of the user's feet or “up” above the user's head. Herein, the point of reference for up and down is the eyeglass frame resting on the user's nose.
One prior art device employs an eyeglass frame where the prism lenses are permanently mounted in a fixed manner on the frames and the user's view is always 90 degrees downward.
U.S. Pat. No. 4,804,261 to Kirschen shows Anti-Claustrophobic Glasses. The Kirschen patent uses angled mirrors that causes image reversal. Also, the mirror angle is not fixed in the Kirschen system so adjustment of the mirror angle to capture the correct image view is time consuming and problematic as angle could change due to vibrations, gravity, and patient movement. An incorrect mirror angle will prevent the patient from seeing intended image target. Further, the Kirschen mirror system may come out of adjustment, that is, change its angular view, during the MRI scan due to MRI system vibration, patient movement or a loose mirror unit. The term MRI as used herein refers to Magnetic Resonance Imaging (MRI), or nuclear magnetic resonance imaging. Kirschen has a back surface mirror mounted on spectacle frame which is attached to the patient's head with an adjustable elastic band. The elastic band requires adjustment for every patient, which takes time and, if not adjusted correctly, could be uncomfortably tight or too loose, causing misalignment of the angled mirror, changing the person's view of the intended target. It is not easy to clean the elastic band that comes in contact with patient hair, potentially enabling the spread of lice, viruses, bacteria and germs
U.S. Pat. No. 5,173,720 to Lee is a Field of View Changer so patients can go in Head-First or Feet-First into the MRI cylinder and maintain visual contact outside the bore to see a projection screen, mural, technologist or friendly face.